In 6 growth hormone-sufficient patients of a pilot study, we have shown synchronicity between nocturnal fluctuations of growth home (GH) and PICP, a serum marker of biosynthesis of type 1 procollagen. We also discovered down-regulation of PICP coincident with the AM rise in cortisol (F). We now intend to further clarify the moduation of PICP by 1: The physiological fluctuation of endogenous GH and F; 2: The administration of exogenous GH; and by 3: The inhibition of endogenous F. We will include profibrotic hormone aldosterone, which also shows diurnal variability in both GH-deficient and GH sufficient patients.